Abstract
Meiosis is crucial in reproduction of plants and ensuring genetic diversity. Although several genes involved in homologous recombination and DNA repair have been reported, their functions in rice (Oryza sativa) male meiosis remain poorly understood. Here, we isolated and characterized the rice OsFIGNL1 (OsFidgetin-like 1) gene, encoding a conserved AAA-ATPase, and explored its function and importance in male meiosis and pollen formation. The rice Osfignl1 mutant exhibited normal vegetative growth, but failed to produce seeds and displayed pollen abortion phenotype. Phenotypic comparisons between the wild-type and Osfignl1 mutant demonstrated that OsFIGNL1 is required for anther development, and that the recessive mutation of this gene causes male sterility in rice. Complementation and CRISPR/Cas9 experiments demonstrated that wild-type OsFIGNL1 is responsible for the male sterility phenotype. Subcellular localization showed that OsFIGNL1-green fluorescent protein was exclusively localized in the nucleus of rice protoplasts. Male meiosis in the Osfignl1 mutant exhibited abnormal chromosome behavior, including chromosome bridges and multivalent chromosomes at diakinesis, lagging chromosomes, and chromosome fragments during meiosis. Yeast two-hybrid assays demonstrated OsFIGNL1 could interact with RAD51A1, RAD51A2, DMC1A, DMC1B, and these physical interactions were further confirmed by BiFC assay. Taken together, our results suggest that OsFIGNL1 plays an important role in regulation of male meiosis and anther development.
Highlights
Male reproductive development is a complex biological process, an understanding of which can lend insight for breeders into traits that increase yield and ensure rice reproductive ability
To ascertain whether female organ development was influenced in the Osfignl1 mutant, a total of 300 embryo sacs of the Osfignl1 plants were examined for female fertility
To prove the interactions further, a BiFC assay demonstrated that OsFIGNL1 interacted with RAD51A1, RAD51A2, DMC1A, and DMC1B in Nicotiana benthamiana leaves cells and interacting proteins had a nuclear localization. These results suggest that rice OsFIGNL1 interacts with rice RAD51A1, RAD51A2, DMC1A, and DMC1B in vivo (Figure 9)
Summary
Male reproductive development is a complex biological process, an understanding of which can lend insight for breeders into traits that increase yield and ensure rice reproductive ability. The anther wall consists of the epidermis, the endothecium, the middle layer and the tapetum (Zhang et al, 2011). The morphology of four somatic layers of the anther wall undergoes dynamic changes, along with the haploid male gametophyte (pollen) generated from diploid pollen mother cells (PMCs) (Tao et al, 2007; Zhang et al, 2011). The formation of pollen grains in plants includes PMC formation, male meiosis, two mitotic processes of microspore and starch filling, and maturation of pollen grains (McCormick, 2004).
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